Power transmitting apparatus, power receiving apparatus, control methods thereof, and program

ABSTRACT

A power transmitting apparatus that transmits power to a power receiving apparatus executes intermittent wireless transmission of power. The power transmitting apparatus operates according to one of a first power transmitting method including detecting a signal load-modulated by the power receiving apparatus using an ID in response to the transmitted power during the intermittent transmission and a second power transmitting method including transmitting the power having modulated the power according to an ID determined in advance so that the power receiving apparatus detects the ID determined in advance.

This application is a continuation of U.S. patent application Ser. No.14/770,773, filed Aug. 26, 2015, which is a national stage applicationof International Patent Application No. PCT/JP2014/059908, filed Mar.28, 2014, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to power transmitting apparatuses, powerreceiving apparatuses, control methods thereof, and programs.

BACKGROUND ART

Widespread research and development of wireless power transmissiontechniques has been underway since Massachusetts Institute of Technology(MIT) successfully demonstrated wireless power transmission usingmagnetic resonance in 2007. Wireless power transmission is alsogarnering attention as a technique that, when combined with wirelesscommunication, enables the realization of a completely wireless system(“Wireless technology developed to transmit power, lights up a 60 W bulbin tests”, Nikkei Electronics, Vol. 966, Dec. 3, 2007). Furthermore,these days, wireless power transmission techniques continue to spread ina variety of applications, such as charging electric automobiles andhybrid automobiles, charging small electronic devices such assmartphones, and so on. For example, Japanese Patent Laid-Open No.2013-38924 discloses a power transmission management apparatus thattransmits power to a vehicle.

With regard to the safe operation of a wireless power transmittingsystem, it is necessary to take into consideration objects that may bepresent in a power transmission-capable area, particularly in systemsthat can transmit power even when a power transmitting apparatus and apower receiving apparatus are distanced from each other, such asmagnetic resonance-based systems. In other words, it is necessary toensure to the greatest extent possible that power will not betransmitted to obstacles that are not power transmission targets, otherunauthenticated devices, and so on located within the powertransmission-capable area of the power transmitting apparatus.Furthermore, it is necessary to suppress heat and the like emitted dueto a drop in efficiency by ensuring that the power transmittingapparatus transmits power only when the power receiving apparatus ispresent in an appropriate location in a relative positional relationshipwith the power transmitting apparatus.

Japanese Patent Laid-Open No. 2013-38924 discloses a method in whichauthentication is carried out between the power transmitting apparatusand the power receiving apparatus before the power transmittingapparatus transmits power, and power transmission is continued afterchecking the consistency between a power amount supplied by the powertransmitting apparatus and a power amount received by a vehicle.However, when using this method, a large amount of power is transmittedand received immediately after the authentication between the powertransmitting apparatus and the power receiving apparatus has ended.Accordingly, there is a problem in that the power transmitting apparatusbegins transmitting power even in the case where the power transmittingapparatus and the power receiving apparatus are not in an appropriatepositional relationship, resulting in a drop in the transmissionefficiency.

The present invention enables wireless power transmission based on thepositional relationship between a power transmitting apparatus and apower receiving apparatus.

SUMMARY OF INVENTION

According to one aspect of the present invention, there is providedpower transmitting apparatus that transmits power to a power receivingapparatus, the power transmitting apparatus comprising: intermittentpower transmission means that executes intermittent wirelesstransmission of power; detection means that detects a load-modulatedsignal received from the power receiving apparatus in response to thepower transmitted by the intermittent power transmission means; andextension means that extends a transmission period of the intermittentpower transmission means in the case where the load-modulated signal hasbeen detected by the detection means.

According to second aspect of the present invention, there is provided apower receiving apparatus that receives power from a power transmittingapparatus, the power receiving apparatus comprising: modulation meansthat repeats load modulation using a signal containing an ID determinedin advance, wherein the load modulation is repeated by the modulationmeans until power transmitted intermittently from the power transmittingapparatus exceeds a predetermined value.

According to third aspect of the present invention, there is provided apower receiving apparatus that receives power from a power transmittingapparatus, the power receiving apparatus comprising: notification meansthat notifies the power transmitting apparatus of an ID determined inadvance through load modulation, wherein the notification is repeated bythe notification means until a notification indicating that the ID hasbeen received is received from the power transmitting apparatus.

According to fourth aspect of the present invention, there is provided apower transmission system comprising a power transmitting apparatus anda power receiving apparatus, wherein the power transmitting apparatusincludes: intermittent power transmission means that executesintermittent wireless transmission of power; detection means thatdetects a load-modulated signal received from the power receivingapparatus in response to the power transmitted by the intermittent powertransmission means; and extension means that extends a transmissionperiod of the intermittent power transmission means in the case wherethe load-modulated signal has been detected by the detection means,wherein the power receiving apparatus includes: modulation means thatrepeats load modulation using a signal containing an ID determined inadvance, and wherein the load modulation is repeated by the modulationmeans until power transmitted intermittently from the power transmittingapparatus exceeds a predetermined value.

According to fifth aspect of the present invention, there is provided acontrol method for a power transmitting apparatus that transmits powerto a power receiving apparatus, the method comprising the steps of:executing intermittent wireless transmission of power; detecting aload-modulated signal received from the power receiving apparatus inresponse to the power transmitted in the step of intermittent wirelesstransmission of power; and extending a transmission period of theintermittent wireless transmission of power in the case where theload-modulated signal has been detected in the step of detecting.

According to sixth aspect of the present invention, there is provided acontrol method for a power receiving apparatus that receives power froma power transmitting apparatus, the method comprising a step of:repeating load modulation using a signal containing an ID determined inadvance, wherein the load modulation is repeated in the step ofrepeating load modulation until power transmitted intermittently fromthe power transmitting apparatus exceeds a predetermined value.

According to seventh aspect of the present invention, there is provideda power transmitting apparatus that transmits power to a power receivingapparatus, the power transmitting apparatus comprising: first powertransmitting means that executes wireless power transmission, whereinthe first power transmitting means executes the power transmission bymodulating power according to an ID determined in advance so that thepower receiving apparatus detects the ID determined in advance.

According to eighth aspect of the present invention, there is provided apower receiving apparatus that receives power from a power transmittingapparatus, the power receiving apparatus comprising: power receivingmeans that receives power wirelessly from the power transmittingapparatus; determination means that determines whether or not an IDdetected based on a state of modulation of a power signal received bythe power receiving means matches an ID determined in advance with thepower transmitting apparatus; and notification means that provides an IDmatch notification to the power transmitting apparatus in the case wherethe determination means has determined that the IDs match.

According to ninth aspect of the present invention, there is provided apower transmission system comprising a power transmitting apparatus anda power receiving apparatus, wherein the power transmitting apparatusincludes: power transmitting means that executes wireless powertransmission, the power transmitting means executing the powertransmission by modulating power according to an ID determined inadvance so that the power receiving apparatus detects the ID determinedin advance, and wherein the power receiving apparatus includes: powerreceiving means that receives an intermittent power signal wirelesslyfrom the power transmitting apparatus; determination means thatdetermines whether or not an ID detected based on a state of the powerreceived by the power receiving means matches an ID determined inadvance with the power transmitting apparatus; and notification meansthat provides an ID match notification to the power transmittingapparatus in the case where the determination means has determined thatthe IDs match.

According to tenth aspect of the present invention, there is provided acontrol method for a power transmitting apparatus that transmits powerto a power receiving apparatus, the method comprising a step of:executing wireless power transmission, wherein in the step of executingwireless power transmission, the power transmission is executed bymodulating power according to an ID determined in advance so that thepower receiving apparatus detects the ID determined in advance.

According to eleventh aspect of the present invention, there is provideda control method for a power receiving apparatus that receives powerfrom a power transmitting apparatus, the method comprising the steps of:receiving power wirelessly from the power transmitting apparatus;determining whether or not an ID detected based on a state of the powerreceived in the step of receiving matches an ID determined in advancewith the power transmitting apparatus; and providing an ID matchnotification to the power transmitting apparatus in the case where ithas been determined in the step of determining that the IDs match.

According to twelfth aspect of the present invention, there is provideda power transmitting apparatus that transmits power to a power receivingapparatus, the power transmitting apparatus comprising: intermittentpower transmission means that executes intermittent wirelesstransmission of power; and selection means that selects one of a firstpower transmitting method including detecting a signal load-modulated bythe power receiving apparatus using an ID in response to the transmittedpower during the intermittent transmission and a second powertransmitting method including transmitting the power having modulatedthe power according to an ID determined in advance so that the powerreceiving apparatus detects the ID determined in advance, wherein thepower transmitting apparatus operates according to the powertransmitting method selected by the selection means.

According to thirteenth aspect of the present invention, there isprovided a control method for a power transmitting apparatus thattransmits power to a power receiving apparatus, the method comprisingthe steps of: executing intermittent wireless transmission of power; andselecting one of a first power transmitting method including detecting asignal load-modulated by the power receiving apparatus using an ID inresponse to the transmitted power during the intermittent transmissionand a second power transmitting method including transmitting the powerhaving modulated the power according to an ID determined in advance sothat the power receiving apparatus detects the ID determined in advance,wherein the power transmitting apparatus operates according to the powertransmitting method selected in the step of selecting.

The present invention enables wireless power transmission based on thepositional relationship between a power transmitting apparatus and apower receiving apparatus.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a wireless power transmitting systemaccording to a first embodiment.

FIG. 2 is a diagram illustrating the configuration of a powertransmitting section in a power transmitting apparatus according to someembodiments.

FIG. 3 is a diagram illustrating the configuration of a power receivingsection in a power receiving apparatus according to a first embodiment.

FIG. 4 is a timing chart of the wireless power transmitting systemaccording to the first embodiment.

FIGS. 5A to 5B are flowcharts illustrating operations performed by thepower transmitting apparatus according to the first embodiment.

FIG. 6 is a flowchart illustrating operations performed by the powerreceiving apparatus according to the first embodiment.

FIG. 7 is a diagram illustrating an appropriate positional relationshipbetween the power transmitting apparatus and the power receivingapparatus.

FIG. 8 is a diagram illustrating the configuration of a powertransmitting section in a power transmitting apparatus according to asecond embodiment.

FIG. 9 is a diagram illustrating the configuration of a power receivingsection in a power receiving apparatus according to the secondembodiment.

FIG. 10 is a timing chart of a wireless power transmitting systemaccording to the second embodiment.

FIGS. 11A to 11B are flowcharts illustrating operations performed by thepower transmitting apparatus according to the second embodiment.

FIG. 12A is a flowchart illustrating operations performed by the powerreceiving apparatus according to the second embodiment.

FIG. 12B is a flowchart illustrating other operations performed by thepower receiving apparatus according to the second embodiment.

FIG. 13 is a diagram illustrating an authentication sequence in awireless power transmitting system according to a third embodiment.

FIG. 14 is a flowchart illustrating operations performed by a powertransmitting apparatus according to the third embodiment.

FIG. 15 is a flowchart illustrating operations performed by a powertransmitting apparatus according to a fourth embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail withreference to the appended drawings. It should be noted that theconfigurations described in the following embodiments are merelyexamples, and that the present invention is not intended to be limitedto the configurations described therein and illustrated in the drawings.

First Embodiment

The present embodiment will be described with reference to the drawings.FIG. 1 is a diagram illustrating a wireless power transmitting systemaccording to the present embodiment. The wireless power transmittingsystem according to the present embodiment includes a power transmittingapparatus 20 and a power receiving apparatus 30. The power transmittingapparatus 20 and the power receiving apparatus 30 include acommunication unit 22 and a communication unit 32, respectively, thatcommunicate wirelessly using Bluetooth®, for example. The communicationunit 22 and the communication unit 32 communicate wirelessly via anantenna 24 and an antenna 34, respectively, by converting digitalsignals transmitted via a communication line 26 and a communication line36, respectively. A power transmitting section 21 in the powertransmitting apparatus 20 converts a DC or AC power input from a powertransmission line 25 into AC frequency power in a transmission band, andtransmits the power via an antenna 23. A power receiving section 31 inthe power receiving apparatus 30 converts the AC power received via anantenna 33 into DC power or AC power in a desired frequency, and outputsthe power to a power transmission line 35.

Power is transmitted over a long distance when transmitting power usinga resonance phenomenon, microwaves, or the like, and thus it isnecessary to pair power transmitting apparatuses with power receivingapparatuses and transmit power to a desired apparatus while preventingpower from being transmitted to other apparatuses and objects. In thepresent embodiment, the power receiving apparatus 30 first searches outthe power transmitting apparatus 20 via the communication unit 32, afterwhich authentication is carried out between the communication unit 32and the communication unit 22. Specifically, in the authentication, IDsare exchanged between the communication unit 32 of the power receivingapparatus 30 and the communication unit 22 of the power transmittingapparatus 20.

FIG. 2 is a block diagram illustrating in detail an example of theinternal configuration of the power transmitting section 21 of the powertransmitting apparatus 20. A CPU 212 includes an initial powertransmitting unit 2121, a power transmission period extension unit 2122,a detection mode signal detecting unit 2123, an ID match determinationunit 2124, a receiving efficiency calculation unit 2125, a normal powertransmitting unit 2126, and an obstacle detection unit 2127. Thefunctions of the respective units in the CPU 212 will be describedlater. A display unit 27 displays information input to the CPU 212 fromthe respective units. A constant power transmitting unit 214 is aconstant voltage source, and a power required to receive power, a powerrequired for an initial power transmission sequence (called an “initialsequence” hereinafter), and the like are set by the initial powertransmitting unit 2121 of the CPU 212. The initial power transmittingunit 2121 may further transmit the initial power in cyclicalintermittent transmission. A switch 215 is used when performing cyclicalintermittent transmission of the initial power in the initial sequence.The switch 215 may be used to send basic data to the power receivingapparatus 30 by turning the switch 215 on and off. Although the switch215 is disposed between the constant power transmitting unit 214 and anAC conversion unit 216 in FIG. 2, any position may be used as long asthe output power can be turned on and off, and thus the switch 215 maybe disposed before the constant power transmitting unit 214, after theAC conversion unit 216, and so on. Furthermore, the AC power output maybe turned on and off by turning a driving signal for a switching element(not shown) within the AC conversion unit 216 on and off, instead ofproviding the switch 215. The AC conversion unit 216 converts DC poweror AC power from an AC outlet or the like into a frequency for powertransmission.

A receiving impedance detection unit 213 detects load modulation carriedout in the power receiving apparatus 30 as well as impedance changes inthe antenna 33, other parts of the power receiving section 31, and soon. The receiving impedance detection unit 213 generally detects thereceiving impedance by detecting reflections caused by mismatchesbetween an impedance on the power transmitting apparatus 20 side,including the transmission antenna 23, and an impedance on the powerreceiving apparatus 30 side. Generally, the efficiency of couplingbetween power transmitting and receiving changes as the positionalrelationship of the power transmitting and receiving apparatuseschanges, and thus reflections caused by mismatches will change even ifthe receiving impedance of the power receiving apparatus 30 remains thesame. However, in the case where a set value such as a unique word isused in the load modulation performed by the power receiving apparatus30, the receiving impedance detection unit 213 can distinguish between achange in the receiving impedance and positional variation. Thereceiving impedance detection unit 213 can also detect objects in apredetermined area around the power transmitting apparatus 20 based onchanges in the impedance on the power transmitting apparatus 20 side,including the transmission antenna 23.

An initial impedance storage unit 217 stores an initial impedanceoccurring when there is nothing in the periphery of the powertransmitting apparatus 20. When, during initial power transmission, thereceiving impedance detection unit 213 detects an impedance that differsfrom the initial impedance without load modulation from the powerreceiving apparatus 30, the obstacle detection unit 2127 stops theinitial power transmission by controlling the switch 215. The obstacledetection unit 2127 then displays an indication that an obstacle hasbeen detected in the display unit 27. An ID storage memory 211 stores anID determined through the device authentication performed by thecommunication unit 22. Meanwhile, the ID match determination unit 2124examines whether or not an ID contained in a detection mode signaldetected by the detection mode signal detecting unit 2123 matches an IDstored in the ID storage memory 211, and sends an ID match notificationin the case where the IDs match.

After the ID match notification has been sent, the power transmittingapparatus 20 performs intermittent transmission for calculating thereceiving efficiency. Upon receiving the intermittent transmission forcalculating the receiving efficiency, the power receiving apparatus 30load-modulates the received power amount or sends the received poweramount to the power transmitting apparatus 20 via the communication unit32. Upon detecting the power amount received by the power receivingapparatus 30 from the receiving impedance detection unit 213 or from thecommunication unit 22, the receiving efficiency calculation unit 2125 ofthe CPU 212 calculates the receiving efficiency by comparing thereceived power amount with the transmitted power. In the case where thereceiving efficiency is lower than a predetermined threshold, thereceiving efficiency calculation unit 2125 displays an indication thatthe receiving efficiency is poor in the display unit 27, and prompts thepower receiving apparatus 30 to be moved to an appropriate position. Onthe other hand, in the case where the receiving efficiency calculationunit 2125 determines that the receiving efficiency exceeds thethreshold, the normal power transmitting unit 2126 starts normal powertransmission.

It is desirable for the power transmission in the initial sequence to beintermittent transmission so that even in the case where power has beentransmitted to an obstacle, a heat dissipation period is provided forthe obstacle in order to suppress a steady rise in temperature caused bycontinuous power transmission. However, power can be transmittedcontinuously in the initial sequence in the case where a sufficientlysmall amount of power is transmitted in the initial sequence and anobstacle is detected for a sufficiently short amount of time in theinitial sequence.

FIG. 3 is a block diagram illustrating in detail an example of theinternal configuration of the power receiving section 31 of the powerreceiving apparatus 30 shown in FIG. 1. A CPU 312 includes a detectionmode signal generating unit 3121, a power calculation unit 3122, and anID match notification receiving unit 3123. The functions of therespective units in the CPU 312 will be described later. A display unit37 displays information input to the CPU 312 from the respective units.314 in the power receiving section 31 indicates an AC power conversionunit, including a rectifier circuit, a constant voltage source, and soon. An impedance changing unit 313 adjusts the alignment of thereceiving antenna 33, and furthermore carries out load modulation usingthe detection mode signal. As long as the authentication by thecommunication unit 32 has not ended, the impedance changing unit 313sets the impedance on the circuit side relative to the receiving antenna33 to a high impedance. The detection mode signal generating unit 3121of the CPU 312 reads out an ID from an ID storage memory 311 that storesthe ID determined through the authentication performed by thecommunication unit 32, and generates the detection mode signal. Theimpedance changing unit 313 carries out load modulation using thegenerated detection mode signal.

Next, operations performed in the initial sequence between the powertransmitting apparatus 20 and the power receiving apparatus 30 will bedescribed with reference to FIG. 4. FIG. 4 is a timing chart for thepower transmitting apparatus 20 and the power receiving apparatus 30. InFIG. 4, the vertical axis for the power transmitting apparatus 20schematically indicates an amount of power transmitted, and the verticalaxis for the power receiving apparatus 30 schematically indicates thereceiving impedance. The following descriptions assume an environment inwhich the power receiving apparatus 30 approaches the power transmittingapparatus 20 in order to receive power, as shown in FIG. 7. FIG. 7indicates a communication area 701, a power transmission area 702, andan area 703 in which power transmission can be carried out at a properefficiency, when the power receiving apparatus 30 approaches the powertransmitting apparatus 20.

When the power receiving apparatus 30 enters the communication area 701of the power transmitting apparatus 20 shown in FIG. 7, the powerreceiving apparatus 30 begins device authentication with the powertransmitting apparatus 20. The power transmitting apparatus 20 and thepower receiving apparatus 30 exchange IDs in the device authentication.When device authentication 400 ends, the power transmitting apparatus 20starts initial power transmission for ID detection at a constant cycle.In the present embodiment, the initial power is transmittedintermittently (T401 to T405). At this time, the initial powertransmitting unit 2121 of the CPU 212 sets the minimum necessary powervalue for the initial sequence leading up to normal power transmission(until ID detection, confirmation of receiving efficiency, and so on inthe frequency band of the power receiving apparatus have ended) in theconstant power transmitting unit 214. Specifically, the initial powertransmitting unit 2121 sets the load modulation of the power receivingapparatus 30 to a power that can be detected by the power transmittingapparatus 20 in an area that includes the area 703 in which powertransmission can be carried out at a proper efficiency.

The power receiving apparatus 30 repeatedly performs load modulationusing the detection mode signal containing the ID exchanged duringdevice authentication 400, which is “1,0,1,0,0,1,0,1” in the exampleshown in FIG. 4 (R401 to R406). In the case where the power transmittingapparatus 20 is distanced from the power receiving apparatus 30 and thelatter is not in an area where power can be received, the transmittedpower is not consumed even if the power receiving apparatus 30 carriesout load modulation, and thus the intermittent transmission in T401 toT404 is almost entirely reflected. When, as the power receivingapparatus 30 approaches the power transmitting apparatus 20, the powerreceiving apparatus 30 enters into the power transmission area 702 shownin FIG. 7, modulated power resulting from the load modulation performedby the power receiving apparatus 30 begins to be transmitted, asindicated by intermittent transmission T405.

In the case where the power transmitting apparatus 20 has begun tomodulate the transmitted power using the ID and intermittenttransmission is underway, the transmission period of the intermittenttransmission is extended to the starting point of the next detectionmode signal, which in FIG. 4 is the starting point of the ID. Althoughthe detection mode signal is configured only of the ID in FIG. 4, itshould be noted that other information may be included as well, such asa start bit sequence, a stop bit sequence, and the like. Furthermore,although for the sake of simplicity FIG. 4 illustrates the detectionmode signal as containing only the ID and the transmission period beingextended based on partial ID detection, the transmission period may beextended based on the partial detection of the detection mode signal.After extending the transmission period of the intermittent transmissionto the starting point of the next detection mode signal, the powertransmitting apparatus 20 furthermore continues to transmit power untilthe end of that detection mode signal in order to obtain the ID. In FIG.4, the power transmitting apparatus 20 continues to transmit power untilthe ID in the next detection mode signal is detected. Thereafter, thepower transmitting apparatus 20 examines whether the detected ID matchesthe ID determined through the device authentication, and in the casewhere the IDs match, the power transmitting apparatus 20 sends an IDmatch notification T406. The ID match notification T406 may be sent fromthe communication unit 22 of the power transmitting apparatus 20 to thecommunication unit 32 of the power receiving apparatus 30, or thetransmitted power may be modulated and transmitted as an ID matchnotification signal by controlling the constant power transmitting unit214, the switch 215, and so on. After the ID match notification is sent,the power transmitting apparatus 20 starts intermittent transmission fordetecting the receiving efficiency (T407 to T409).

Upon receiving the intermittent power after detecting the ID matchnotification after the power from the power transmitting apparatus 20has exceeded a predetermined value, the power receiving apparatus 30measures the received power each time the power is intermittentlyreceived, and carries out the load modulation using that value (R407 toR409). The power transmitting apparatus 20 may detect the received powervalue from the load modulation value and calculate the receivingefficiency by comparing the power sent by the power transmittingapparatus 20 with the power that has been received. In the example shownin FIG. 4, the receiving efficiency exceeds a predetermined threshold atthe third intermittent transmission T409; it is determined that thepower receiving apparatus 30 has entered the area 703 for transmissionat the appropriate efficiency indicated in FIG. 7, and the powertransmission switches to normal power transmission T410. Although inFIG. 4, the power receiving apparatus 30 sends the received power amountthrough load modulation, it should be noted that the received poweramount may be transmitted from the communication unit 32 to thecommunication unit 22 of the power transmitting apparatus 20.

Note also that although the power transmitting apparatus 20 starts theintermittent transmission for measuring the receiving efficiency afterthe ID matching notification T406 in FIG. 4, the method for measuringthe receiving efficiency is not limited thereto. That is, the powerreceiving apparatus 30 may notify the power transmitting apparatus 20 ofthe received power amount when at low impedance during the loadmodulation based on the detection mode signal, or in other words, when“0” is sent at R406, may detect the received power amount when the IDmatching notification T406 is received and notify the power transmittingapparatus 20, and so on. Methods such as load modulation during IDmatching notification and out-of-band communication using thecommunication unit 32 can be considered as methods for giving notice ofthe received power amount. Alternatively, another transmission periodmay be provided after the ID matching notification, and notice of thereceived power amount may be given then. It is clear that intermittenttransmission for detecting the receiving efficiency is unnecessary ifthe power received during modulation based on the detection mode signal,when the ID match notification is made, and so on exceeds thepredetermined threshold.

Next, operations performed by the power transmitting apparatus 20 willbe described with reference to FIGS. 2 and 5. FIG. 5 is an example of aflowchart illustrating operations performed by the power transmittingapparatus 20, from device authentication to normal power transmission.When the transmitting/receiving device authentication is complete(S501), the initial power transmitting unit 2121 sets the transmissionpower of the constant power transmitting unit 214 to an initial settingpower (S502), and starts the initial power transmission for ID detection(S503). When intermittent transmission is carried out, the initial poweris intermittently transmitted using the switch 215. The receivingimpedance detection unit 213 continually monitors the impedance duringthe period of intermittent transmission, and a device that has beenload-modulated using the detection mode signal including the IDdetermined in device authentication S501 is detected. Here, the initialimpedance storage unit 217 stores, in advance, an initial impedanceoccurring in a state where devices that can receive power at thetransmitted frequency, obstacles such as metal, and so on are notpresent in the periphery of the power transmitting apparatus 20.

In the case where the receiving impedance detection unit 213 hasdetected an impedance that differs from the initial impedance (Yes inS504), the obstacle detection unit 2127 determines that an obstacle ispresent. Specifically, the obstacle detection unit 2127 determines thatan obstacle has been detected in the case where an impedance that couldnot result from the load modulation using the aforementioned ID has beendetected (Yes in S505). Then, the receiving impedance detection unit 213stops the transmission of power by controlling the switch 215 via theCPU 212 (S516) and displays an error, indicating that an obstacle hasbeen detected, in the display unit 27 (S517). For example, in the casewhere the receiving impedance detection unit 213 has detected a constantimpedance that differs from the initial impedance, it is possible that ametal object or the like has approached; an indication that a metalobject is present is then displayed in the display unit 27, prompting auser to move the object. Likewise, in the case where the receivingimpedance detection unit 213 has detected a load modulation in adifferent format than the power receiving apparatus 30, a differentmodel of a power receiving apparatus, a device communicating in the sameband, or the like is present in the vicinity; an indication thereof isthen displayed in the display unit 27, prompting the user to move thedevice. Here, the power transmitting apparatus 20 has stoppedtransmitting power, and thus after the user has removed the obstacle, anoperation such as the user pushing a button (not shown) indicating thatthe obstacle has been removed is detected (S518), and the processreturns to the initial power transmission for ID detection (S503).However, in the case where the power transmitted in the initial powertransmission for ID detection is sufficiently low or the amount of timefor which the obstacle is detected is sufficiently short and there islittle likelihood of damage caused by the obstacle emitting heat orreceiving power (No in S504, No in S505), the process may return to theinitial power transmission for ID detection (S503) without the userperforming such a restoration operation.

In the case where the impedance detected by the receiving impedancedetection unit 213 is the same as the initial impedance and thedetection mode signal detecting unit 2123 has partially detected thedetection mode signal (Yes in S504), the process advances to S506 in thecase where the initial power is being intermittently transmitted. Then,the power transmission period extension unit 2122 extends the period ofthe intermittent transmission to a time at which the starting point ofthe next detection mode signal is detected (S506). The process of S506is unnecessary in the case where the initial power is being continuouslytransmitted. Here, in the case where the starting point of the nextdetection mode signal is not detected within a set period, it ispossible that the detection mode signal detecting unit 2123 has detectedthe load modulation of, for example, a power receiving apparatusoperating according to another standard, or that the desired powerreceiving apparatus 30 has left the area. In this case, the detectionmode signal detecting unit 2123 makes an error display in the displayunit 27, prompting the user to respond (S519). Thereafter, the processreturns to the initial power transmission for ID detection, and it isconfirmed that the device operating according to another standard hasbeen removed or that the desired power receiving apparatus 30 has beendetected. In the case where the detection mode signal detecting unit2123 has detected the starting point of the detection mode signal (Yesin S507) and the initial power is being intermittently transmitted, thepower transmission period extension unit 2122 extends the transmissionperiod until the detection mode signal ends (S508). Here, in the casewhere the starting point of the detection mode signal has been detectedin S504, it follows that the starting point of the detection mode signalhas already been detected in S507, and thus the transmission period canbe extended until the detection mode signal ends.

The ID match determination unit 2124 examines whether the ID determinedin the device authentication matches the ID detected from the detectionmode signal (S509). In the case where the IDs differ (No in S509), it ispossible that a different power receiving apparatus operating accordingto the same standard and that has completed authentication with anotherpower transmitting apparatus is present in the vicinity, and thus adisplay to that effect is made in the display unit 27, prompting theuser to move the apparatus (S519). Thereafter, the process returns tothe initial power transmission for ID detection, and it is confirmedthat the other power receiving apparatus operating according to the samestandard has been removed. In the case where the ID match determinationunit 2124 has determined that the IDs match (Yes in S509), an ID matchnotification is sent (S510). The ID match determination unit 2124 maysend the ID match notification from the communication unit 22 to thecommunication unit 32 of the power receiving apparatus 30, or bycontrolling the constant power transmitting unit 214, the switch 215,and so on, the transmitted power may be modulated and transmitted as anID matching notification signal. After the ID match notification hasbeen sent, the initial power transmitting unit 2121 starts theintermittent transmission for detecting the receiving efficiency (S511).Upon receiving the intermittently-transmitted power, the power receivingapparatus 30 measures the power received with each reception and carriesout load modulation at that value. The receiving efficiency calculationunit 2125 detects the received power value from the load modulationvalue (S512) and calculates the receiving efficiency by comparing thepower the power transmitting apparatus 20 has sent with the power thathas been received (S513). In the case where the receiving efficiency isless than or equal to a predetermined threshold, the receivingefficiency calculation unit 2125 determines that the power receivingapparatus 30 is not within the area 703 for transmission at theappropriate efficiency indicated in FIG. 7, and displays, in the displayunit 27, a recommendation for moving the power receiving apparatus intoa proper position (S520). However, in the case where the receivingefficiency exceeds the threshold, the receiving efficiency calculationunit 2125 determines that the power receiving apparatus is within thearea 703 for transmission at the appropriate efficiency, and the processis switched to normal power transmission by the normal powertransmitting unit 2126 (S515).

Next, operations performed by the power receiving apparatus 30 will bedescribed with reference to FIGS. 3 and 6. FIG. 6 is an example of aflowchart illustrating operations performed by the power receivingapparatus 30, from device authentication to normal power transmission.The impedance changing unit 313 sets the impedance of the antenna 33 ora load (not shown) (that is, the receiving impedance) to a higher leveluntil the device authentication (S602) with the power transmittingapparatus 20 ends, and ensures that power will not be received from apower transmitting apparatus operating according to another standard, anunauthorized power transmitting apparatus operating according to thesame standard, and so on (S601). This prevents heat emission, damage,and so on in the power receiving apparatus. After the deviceauthentication (S602), the power receiving apparatus 30 carries out loadmodulation using the detection mode signal including the IDs exchangedin the device authentication (S603). This detection mode signal isgenerated by the detection mode signal generating unit 3121. This loadmodulation may be carried out by the impedance changing unit 313 shownin FIG. 3, or may be carried out by changing the load of the AC powerconversion unit 314. The load modulation may further be carried out byturning an antenna switch (not shown) on and off.

Although the power receiving apparatus 30 will receive almost no powerwhile the power receiving apparatus 30 is far from the powertransmitting apparatus 20 (No in S604), when the power receivingapparatus 30 approaches the power transmitting apparatus 20 and entersthe power transmission area 702 shown in FIG. 7, the power transmittedby the power transmitting apparatus 20 is modulated according to theload modulation of the power receiving apparatus 30 and is then received(Yes in S604). In other words, a state of power detection is achieved.If the apparatus transmitting power is the apparatus authenticated inthe device authentication (S602), the ID match notification is sent fromthe power transmitting apparatus 20 after the load modulation of thedetection mode signal performed by the power receiving apparatus 30 hasended (S603, Yes in S604). Accordingly, the impedance changing unit 313sets the receiving impedance to an impedance at which the ID matchnotification can be received after the modulation using the nextdetection mode signal after power has been detected is complete (S605).However, the ID match notification may be carried out using thecommunication units 22 and 23. Although the detection mode signalmodulation stops after the power is detected in FIG. 6, it should benoted that the detection mode signal modulation may continue until theID match notification is received. Furthermore, in the case where the IDmatch notification is sent and received using the communication units 22and 32, the impedance changing unit 313 may increase the receivingimpedance after the detection mode signal modulation ends.

Meanwhile, in the case where the ID match notification is not receivedeven after power is detected (No in S606), it is possible that power isbeing transmitted from a power transmitting apparatus operatingaccording to another standard or that power is being received from adifferent power transmitting apparatus of the same model, and thus anerror is displayed in the display unit 37 (S611), prompting the user tomove the power receiving apparatus 30 to another position. In the casewhere the power receiving apparatus 30 has received the ID matchnotification (Yes in S606), the impedance changing unit 313 reduces thereceiving impedance (S607) and receives the intermittent transmission ofpower for calculating the receiving efficiency. The power receivingapparatus 30 replies with an indication of the received power throughload modulation, or replies with information indicating the receivedpower via the communication units 32 and 22, each time power is received(S608). However, the power receiving apparatus 30 only returns anotification of the received power through load modulation, or makes areply indicating the received power via the communication units 32 and22, each time power is received (S611), and this process continues untilit is determined that power is to be continuously received (No in S609).When it is determined that power is to be continuously received (Yes inS609), the normal power receiving (S610) begins.

In this manner, the power transmitting apparatus 20 according to thepresent embodiment does not start transmitting power unless atransmission target that has been authenticated has entered a desiredarea where power can be supplied and the transmission target matches adesired transmission target. This makes it possible to prevent theemission of heat, damage due to power being transmitted, and so on innon-transmission targets. Furthermore, the power receiving apparatus 30according to the present embodiment reduces the receiving impedance onlyin the case where power is supplied from an authenticated powertransmitting apparatus, which makes it possible to prevent theunnecessary receiving of power from an unauthenticated device and reducethe possibility of damage to the device.

Although the present embodiment describes the power transmittingapparatus 20 as starting normal power transmission in the case where thereceiving efficiency is greater than or equal to a threshold after an IDmatch has been determined, the normal power transmission may simply bestarted after the ID match has been determined. In addition, althoughthe power transmitting apparatus 20 determines the appropriatepositional relationship with the power receiving apparatus 30 based onthe receiving efficiency that can be calculated from the power receivedby the power receiving apparatus 30, a value aside from the receivingefficiency may be used for this determination as long as it is a valueobtained based on the power received by the power receiving apparatus30. Finally, although the present embodiment describes the powertransmitting apparatus intermittently transmitting power in order tocalculate the receiving efficiency, a process for calculating thereceiving efficiency through continuous power transmission may becarried out.

Second Embodiment

The present embodiment will be described with reference to the drawings.A wireless power transmitting system according to the present embodimentis the same as the system illustrated in FIG. 1 and described in thefirst embodiment, and thus descriptions thereof will be omitted. Thepower transmitting apparatus 20 and the power receiving apparatus 30according to the present embodiment differ from those described in thefirst embodiment in terms of the power transmitting section 21 and thepower receiving section 31.

FIG. 8 is a block diagram illustrating in detail an example of theinternal configuration of the power transmitting section 21 of the powertransmitting apparatus 20. A CPU 812 includes an initial powertransmitting unit 8121, a detection mode signal generation unit 8122, anID match notification receiving unit 8123, a receiving efficiencycalculation unit 8124, a normal power transmitting unit 8125, and anobstacle detection unit 8126. The functions of the respective units inthe CPU 812 will be described later. The display unit 27 displaysinformation input to the CPU 812 from the respective units. A constantpower transmitting unit 814 is a constant voltage source, and a powerrequired to receive power, a power required for an initial powertransmission sequence (called an “initial sequence” hereinafter), andthe like are set by the initial power transmitting unit 8121 of the CPU812. The initial power transmitting unit 8121 may further transmit theinitial power in cyclical intermittent transmission. The powertransmitting apparatus 20 can also send basic data to the powerreceiving apparatus 30 by modulating the output of the constant powertransmitting unit 814.

A switch 815 is used when performing cyclical intermittent transmissionof the initial power in the initial sequence. The switch 815 may be usedto send basic data to the power receiving apparatus 30 by turning theswitch 815 on and off. An AC conversion unit 816 converts DC power or ACpower from an AC outlet or the like into a frequency for powertransmission. Although the switch 815 is disposed between the constantpower transmitting unit 814 and the AC conversion unit 816 in FIG. 8,any position may be used as long as the output power can be turned onand off, and thus the switch 815 may be disposed before the constantpower transmitting unit 814, after the AC conversion unit 816, and soon. Furthermore, the AC power output may be turned on and off by turninga driving signal for a switching element (not shown) within the ACconversion unit 816 on and off, instead of providing the switch 815. TheAC conversion unit 816 converts DC power or AC power from an AC outletor the like into a frequency for power transmission.

A receiving impedance detection unit 813 detects load modulation carriedout in the power receiving apparatus 30 as well as impedance changes inthe antenna 33, other parts of the power receiving section 31, and soon. The receiving impedance detection unit 813 generally detects thereceiving impedance by detecting reflections caused by mismatchesbetween an impedance on the power transmitting apparatus 20 side,including the transmission antenna 23, and an impedance on the powerreceiving apparatus 30 side. Generally, the efficiency of couplingbetween power transmitting and receiving changes as the positionalrelationship of the power transmitting and receiving apparatuseschanges, and thus reflections caused by mismatches will change even ifthe receiving impedance of the power receiving apparatus 30 remains thesame. However, the receiving impedance detection unit 813 candistinguish between a change in the receiving impedance and positionalvariation by the power receiving apparatus 30 replying with a signal orthe like indicating power reception through load modulation.

An initial impedance storage unit 817 stores an initial impedanceoccurring when there is nothing in the periphery of the powertransmitting apparatus 20. When, during initial power transmission, thereceiving impedance detection unit 813 detects an impedance that differsfrom the initial impedance without load modulation from the powerreceiving apparatus 30, the obstacle detection unit 8126 stops theinitial power transmission by controlling the switch 815. The obstacledetection unit 8126 then displays an error display indicating that anobstacle has been detected in the display unit 27. An ID storage memory811 stores an ID determined through the device authentication performedby the communication unit 22. The detection mode signal generation unit8122 generates the detection mode signal based on the ID stored in theID storage memory 811. The output of the constant power transmittingunit 814 is modulated using the generated detection mode signal andtransmitted. Note that power modulated using the detection mode signalby turning the switch 815 on and off may be transmitted.

The power receiving apparatus 30 that has been authenticated receivesthe transmitted power modulated using the detection mode signal, andupon confirming an ID match, sends an ID match notification. The powertransmitting apparatus 20 receives the ID match notification throughload modulation of the transmitted power or via the communication unit22. When the ID match notification receiving unit 8123 receives the IDmatch notification, the power transmitting apparatus 20 can confirm thatthe power receiving apparatus 30 has entered an area in which power canbe received from the power transmitting apparatus 20.

After the ID match notification has been received, the powertransmitting apparatus 20 performs intermittent transmission forcalculating the receiving efficiency. Upon receiving the intermittenttransmission for calculating the receiving efficiency, the powerreceiving apparatus 30 load-modulates the received power amount or sendsthe received power amount to the power transmitting apparatus 20 via thecommunication unit 32. Upon detecting the power amount received by thepower receiving apparatus 30 from the receiving impedance detection unit813 or from the communication unit 22, the receiving efficiencycalculation unit 8124 of the CPU 812 calculates the receiving efficiencyby comparing the received power amount with the transmitted power. Inthe case where the receiving efficiency is lower than a predeterminedthreshold, the receiving efficiency calculation unit 8124 displays anindication that the receiving efficiency is poor in the display unit 27,and prompts the power receiving apparatus 30 to be moved to anappropriate position. On the other hand, in the case where the receivingefficiency calculation unit 8124 determines that the receivingefficiency exceeds the threshold, the normal power transmitting unit8125 starts normal power transmission. It is desirable for the powertransmission in the initial sequence to be intermittent transmission sothat even in the case where power has been transmitted to an obstacle, aheat dissipation period is provided for the obstacle in order tosuppress a steady rise in temperature caused by continuous powertransmission. For example, transmitted power modulated during adetection mode signal period and a stopped period for dissipating heatin an obstacle is taken as a single cycle of power transmission.However, power can also be transmitted continuously in the initialsequence in the case where a sufficiently small amount of power istransmitted in the initial sequence and an obstacle is detected for asufficiently short amount of time in the initial sequence, and thedetection mode signal includes breaks such as a start bit, a stop bit,and so on.

FIG. 9 is a block diagram illustrating in detail an example of theinternal configuration of the power receiving section 31 of the powerreceiving apparatus 30 shown in FIG. 1. A CPU 912 includes a detectionmode signal determination unit 9121, a power calculation unit 9122, andan ID match notification generation unit 9123. The functions of therespective units in the CPU 912 will be described later. The displayunit 37 displays information input to the CPU 912 from the respectiveunits. An AC power conversion unit 914 includes a rectifier circuit, aconstant voltage source, and so on. An impedance changing unit 913adjusts the alignment of the receiving antenna 33, and furthermorecarries out load modulation in the case where data is to be transmittedto the power transmitting apparatus using the powertransmission/receiving frequency band. As long as the authentication bythe communication unit 32 has not ended, the impedance changing unit 913sets the impedance on the circuit side relative to the receiving antenna33 to a high impedance. The receiving impedance is reduced when theauthentication by the communication unit 32 has ended.

An ID storage memory 911 stores an ID determined through theauthentication performed by the communication unit 32. When thecommunication unit 32 detects a power signal from the power transmittingapparatus 20, the detection mode signal determination unit 9121determines whether or not that signal is the detection mode signal. Inthe case where the signal is the detection mode signal and the IDcontained in the detection mode signal matches the ID stored in the IDstorage memory 911, the ID match notification generation unit 9123generates an ID matching notification and sends the notification to thepower transmitting apparatus 20. Furthermore, the power calculation unit9122 calculates the received power amount detected by the AC powerconversion unit 914 and sends the received power amount to the powertransmitting apparatus 20 through load modulation or via thecommunication unit 32.

Next, operations performed in the initial sequence between the powertransmitting apparatus 20 and the power receiving apparatus 30 will bedescribed with reference to FIG. 10. FIG. 10 is a timing chart for thepower transmitting apparatus 20 and the power receiving apparatus 30. InFIG. 10, the vertical axis for the power transmitting apparatus 20schematically indicates an amount of power transmitted, and the verticalaxis for the power receiving apparatus 30 schematically indicates anamount of power received. Meanwhile, ZR01 to ZR03 for the powerreceiving apparatus 30 indicate that the receiving impedance is set to ahigh value. Note that the following descriptions assume an environmentin which the power receiving apparatus 30 approaches the powertransmitting apparatus 20 in order to receive power, as shown in FIG. 7.FIG. 7 indicates the communication area 701, the power transmission area702, and the area 703 in which power transmission can be carried out ata proper efficiency, when the power receiving apparatus 30 approachesthe power transmitting apparatus 20.

When the power receiving apparatus 30 enters the communication area 701of the power transmitting apparatus 20 shown in FIG. 7, the powerreceiving apparatus 30 begins device authentication with the powertransmitting apparatus 20. The power transmitting apparatus 20 and thepower receiving apparatus 30 exchange IDs in the device authentication.When device authentication 1000 ends, the power transmitting apparatus20 starts initial power transmission of power modulated using thedetection mode signal at a constant cycle (T1001 to T1007). In theexample shown in FIG. 10, the power transmitting apparatus 20 cyclicallytransmits power modulated using the detection mode signal containing theexchanged ID “1,0,1,0,0,1,0,1”. At this time, the initial powertransmitting unit 8121 of the CPU 812 sets the minimum necessary powervalue for the initial sequence leading up to normal power transmission(until ID detection, confirmation of receiving efficiency, and so on inthe frequency band of the power receiving apparatus have ended) in theconstant power transmitting unit 814. Specifically, the initial powertransmitting unit 8121 sets the power modulated using the detection modesignal of the power transmitting apparatus 20 to a power that can bereceived by the power receiving apparatus 30 in an area that includesthe area 703 in which power transmission can be carried out at a properefficiency. Note that the initial power transmitting unit 8121 may carryout intermittent transmission of the initial power modulated by thedetection mode signal, as indicated in FIG. 4.

The power receiving apparatus 30 increases the receiving impedance untilthe end of device authentication 1000 (ZR01). After the deviceauthentication, the power receiving apparatus 30 changes the impedanceto a low impedance, and stands by for the transmission of powermodulated using the detection mode signal including the ID determinedthrough the device authentication, which is “1,0,1,0,0,1,0,1” in theexample shown in FIG. 10. In the case where the power transmittingapparatus 20 is distanced from the power receiving apparatus 30 and thelatter is not in an area where power can be received, the transmittedpower is not consumed even if the power receiving apparatus 30 stands byat low impedance, and thus the intermittent transmission in T1001 toT1004 is almost entirely reflected. When, as the power receivingapparatus 30 approaches the power transmitting apparatus 20, the powerreceiving apparatus 30 enters into the power transmission area 702 shownin FIG. 7, power begins to be transmitted to the power receivingapparatus 30, as indicated by intermittent transmission T1005.

After the device authentication using the communication unit 32, thepower receiving apparatus 30 stands by for power transmission at lowimpedance. Upon receiving power not modulated using the detection modesignal as indicated by R1001, the power receiving apparatus 30 increasesthe receiving impedance as indicated by ZR02, preventing the powerreceiving apparatus from being damaged or emitting heat due to a powersupply from another apparatus. Furthermore, the power receivingapparatus 30 displays an indication that power is being supplied fromanother apparatus in the display unit 37, prompting the user to move thepower receiving apparatus 30 away from the other power transmittingapparatus. The power receiving apparatus 30 reduces the receivingimpedance again when a restoration operation performed by the user, suchas the user pressing a button (not shown), has been detected. Here, ifthe amount of power received from the other device does not result inheat emission above a permitted amount, and if the power is at a levelthat does not cause damage to the circuitry of the power receivingapparatus 30, it is unnecessary for the power receiving apparatus 30 toincrease the receiving impedance, and unnecessary for the user toperform restoration operations.

In the case where the power receiving apparatus 30 has received powerR1006 modulated using the detection mode signal after part R1005 of theID contained in the detection mode signal has been detected, the IDcontained in the detection mode signal is detected from a pattern ofchange of the received amount of the power R1006. The power receivingapparatus 30 then determines whether or not the detected ID matches theID determined in the device authentication. In the case where the IDsmatch, the power receiving apparatus 30 sends an ID match notificationR1007 to the power transmitting apparatus 20. Although FIG. 10illustrates an example in which the power transmitting apparatus 20 isnotified of an ID match through load modulation performed by changingthe receiving impedance of the received power R1007 associated withtransmitted power T1007 as indicated by ZR03, it should be noted thatthe ID detection notification may be made via the communication unit 32.Furthermore, although the detection mode signal is configured only of anID in FIG. 10, the signal may include other information such as a startbit, a stop bit, or the like.

After detecting the ID match notification, the power transmittingapparatus 20 starts intermittent transmission for detecting thereceiving efficiency (T1008 to T1010). Upon receiving theintermittently-transmitted power from the power transmitting apparatus20 after making the ID match notification, the power receiving apparatus30 measures the power received with each reception and carries out loadmodulation at that value (R1008 to R1010). The power transmittingapparatus 20 may detect the received power value from the loadmodulation value and calculate the receiving efficiency by comparing thepower the power transmitting apparatus 20 has sent with the power thathas been received. In the example shown in FIG. 10, the receivingefficiency exceeds a predetermined threshold at the third intermittenttransmission T1010; it is determined that the power receiving apparatus30 has entered the area 703 for transmission at the appropriateefficiency indicated in FIG. 7, and the power transmission switches tonormal power transmission T1011. Although the power receiving apparatus30 sends the received power amount through load modulation in FIG. 10,the received power amount may be transmitted to the communication unit22 of the power transmitting apparatus 20 from the communication unit32.

Note also that although the power transmitting apparatus 20 starts theintermittent transmission for measuring the receiving efficiency afterthe ID matching notification T1007 has been received in FIG. 10, themethod for measuring the receiving efficiency is not limited thereto. Inother words, the power receiving apparatus 30 may notify the powertransmitting apparatus 20 of the received power amount at the ID matchnotification T1006 and the reception T1007, or in other words, bydetecting the received power amount at R1006 and R1007. Methods such asload modulation during ID matching notification and out-of-bandcommunication using the communication unit 32 can be considered asmethods for giving notice of the received power amount. It is clear thatintermittent transmission for detecting the receiving efficiency isunnecessary if the power received during modulation based on thedetection mode signal, when the ID match notification is detected, andso on exceeds the predetermined threshold.

Next, operations performed by the power transmitting apparatus 20 willbe described with reference to FIGS. 8 and 11. FIG. 11 is an example ofa flowchart illustrating operations performed by the power transmittingapparatus 20, from device authentication to normal power transmission.When the transmitting/receiving device authentication is complete(S1101), the initial power transmitting unit 8121 sets the transmissionpower of the constant power transmitting unit 814 to an initial settingpower (S1102), and starts the initial power transmission as modulatedusing the detection mode signal (S1103). When the intermittenttransmission is carried out, the initial power modulated using thedetection mode signal as described above may be transmittedintermittently using the switch 815. The receiving impedance detectionunit 813 continually monitors the impedance during the period of initialpower transmission, and a device that has been load-modulated using thedetection mode signal including the ID determined in deviceauthentication S1101 is detected. Here, the initial impedance storageunit 817 stores, in advance, an initial impedance occurring in a statewhere devices that can receive power at the transmitted frequency,obstacles such as metal, and so on are not present in the periphery ofthe power transmitting apparatus 20.

In the case where the receiving impedance detection unit 813 hasdetected an impedance that is different from the initial impedance (Yesin S1104), the power transmitting apparatus 20 stands by for greaterthan or equal to the sending cycle of the detection mode signal whilecontinuing the initial power transmission (S1105). Here, in the casewhere the ID match notification receiving unit 8123 does not receive theID match notification from the power receiving apparatus 30 (No inS1106), the power transmission is stopped by controlling the switch 815(S1107) and a display indicating that an obstacle has been detected ismade via the display unit 27 (S1108). For example, it is possible that ametal object or the like has approached in the case where a constantimpedance that differs from the initial impedance is detected, and thusan indication that a metal object is present is displayed, prompting theuser to move the object. Likewise, in the case where the receivingimpedance detection unit 813 has detected a load modulation in adifferent format than the reply from the power receiving apparatus 30, adifferent model power receiving apparatus, a device communicating in thesame band, or the like is present in the vicinity; an indication thereofis then displayed, prompting the user to move the device. Here, thepower transmitting apparatus 20 has stopped transmitting power, and thusafter the user has removed the obstacle, an operation such as the userpushing a button (not shown) indicating that the obstacle has beenremoved is detected (S1109), and the process returns to the initialpower transmission modulated using the detection mode signal (S1103).However, in the case where the power transmitted in the initial powertransmission is sufficiently low or the amount of time for which theobstacle is detected is sufficiently short and there is littlelikelihood of damage caused by the obstacle emitting heat or receivingpower, the process may return to the initial power transmission (S1103)without the power transmission being stopped and without the userperforming such a restoration operation.

In the case where the ID match notification receiving unit 8123 hasreceived the ID match notification after the receiving impedancedetection unit 813 has detected a change in the impedance (Yes inS1106), the initial power transmitting unit 8121 starts intermittenttransmission for calculating the received power (S1111). Here, normally,the power transmitting apparatus 20 detects a change in the impedancewhen the power receiving apparatus 30 receives power modulated using thedetection mode signal. However, in the case where the signal detectionsensitivity of the power receiving apparatus 30 is higher than thesensitivity at which the power transmitting apparatus 20 detects achange in the impedance, it is possible that the power transmittingapparatus 20 will detect the ID match notification from the powerreceiving apparatus even if a change in the impedance cannot bedetected. In this manner, the power transmitting apparatus starts theintermittent transmission for calculating the received power (S1111) inthe case where the receiving impedance detection unit 813 does notdetect a change in the impedance (No in S1104) and the ID matchnotification receiving unit 8123 has detected the ID match notification(S1110). Note that in the case where the receiving impedance detectionunit 813 does not detect a change in the impedance and the ID matchnotification receiving unit 8123 does not detect the ID matchnotification, the initial power transmitting unit 8121 continues theinitial power transmission modulated using the detection mode signal (Noin S1104, No in S1110).

Upon receiving the intermittently-transmitted power for calculating thereceived power, the power receiving apparatus 30 measures the powerreceived with each reception and carries out load modulation at thatvalue. The receiving efficiency calculation unit 8124 detects thereceived power value from the load modulation value (S1112) andcalculates the receiving efficiency by comparing the power sent by thepower transmitting apparatus 20 with the power that has been receivedusing a comparison unit (not shown) in the CPU 812 (S1113). In the casewhere the receiving efficiency is less than or equal to a predeterminedthreshold, the receiving efficiency calculation unit 8124 determinesthat the power receiving apparatus 30 is not within the area 703 fortransmission at the appropriate efficiency indicated in FIG. 7, anddisplays, in the display unit 27, a recommendation for moving the powerreceiving apparatus into a proper position (S1115). However, in the casewhere the receiving efficiency exceeds the threshold, the receivingefficiency calculation unit 8124 determines that the power receivingapparatus is within the area 703 for transmission at the appropriateefficiency, and the process is switched to normal power transmission bythe normal power transmitting unit 8125 (S1116).

Next, operations performed by the power receiving apparatus 30 will bedescribed with reference to FIGS. 9, 12A, and 12B. FIG. 12A is anexample of a flowchart illustrating operations performed by the powerreceiving apparatus 30, from device authentication to normal powertransmission. The impedance changing unit 913 sets the impedance of theantenna 33 or a load (not shown) (that is, the receiving impedance) to ahigher level until the device authentication (S1202) with the powertransmitting apparatus 20 ends, and ensures that power will not bereceived from a power transmitting apparatus operating according toanother standard, an unauthorized power transmitting apparatus operatingaccording to the same standard, and so on (S1201). This prevents heatemission, damage, and so on in the power receiving apparatus. After thedevice authentication carried out through the communication unit 32, theimpedance changing unit 913 reduces the receiving impedance (S1203) andstands by until power is detected (No in S1204).

In the case where the power receiving section 31 has detected power (Yesin S1204), the detection mode signal determination unit 9121 determineswhether or not the received power is modulated using the detection modesignal containing the ID determined during authentication. In otherwords, the detection mode signal determination unit 9121 obtains the IDfrom the received power and determines whether or not the obtained IDmatches the ID stored in the ID storage memory 911. In the case wherethe detection mode signal determination unit 9121 determines that theIDs do not match (No in S1205), the impedance changing unit 913increases the receiving impedance (S1206). Doing so prevents damage, theemission of heat, and so on caused by the power receiving apparatus 30being supplied with power from another apparatus. Furthermore, thedetection mode signal determination unit 9121 displays an indicationthat the power is supplied from another apparatus in the display unit 37(S1207), prompting the user to distance the power receiving apparatus 30from the other power transmitting apparatus. The power receivingapparatus 30 then detects a restoration operation performed by the user,such as the user pressing a button (not shown) (S1208), and theimpedance changing unit 913 reduces the receiving impedance again(S1209). Here, if the amount of power received from the other apparatusdoes not result in heat emission above a permitted amount, and if thepower is at a level that does not cause damage to the circuitry of thepower receiving apparatus 30, it is unnecessary to increase thereceiving impedance in S1206, and unnecessary to detect the userrestoration operation completion in S1208. Furthermore, the receivingimpedance has not advanced and thus it is not necessary to reduce theimpedance in S1209.

On the other hand, in the case where the power receiving section 31 hasdetected power (Yes in S1204) and the detection mode signaldetermination unit 9121 has determined that the IDs match (Yes inS1205), the ID match notification generation unit 9123 generates the IDmatch notification and sends the notification to the power transmittingapparatus 20 (S1210). The sending of the ID match notification may becarried out using load modulation, or may be carried out via thecommunication unit 32. After the ID match notification has been sent,the power receiving apparatus 30 receives the intermittent transmissionof power for calculating the receiving efficiency. However, the powerreceiving apparatus 30 only returns a notification of the received powerthrough load modulation or via the communication units 32 and 22 eachtime power is received (S1211), and this process continues until acontinuous receiving determination unit (not shown) in the CPU 912determines that power is to be continuously received (No in S1212). Whenit is determined that power is to be continuously received (Yes inS1212), the normal power receiving (S1213) begins.

FIG. 12B is a flowchart illustrating another procedure for setting theimpedance performed by the power receiving apparatus 30. After thedevice authentication (S1202), the impedance changing unit 913 sets thereceiving impedance to an intermediate value (S1214). Meanwhile, in thecase where the IDs do not match (No in S1205) and the impedance changingunit 913 has increased the receiving impedance, the receiving impedanceis set to the intermediate value after a restoration operation has beenperformed by the user (S1215). The impedance changing unit 913 changesthe receiving impedance to a low impedance for normal power receivingfor the first time after the ID match notification has been sent(S1216). As a result, the power receiving apparatus 30 does not go tothe low impedance unless the IDs are confirmed in the power transmissionband, which reduces heat emission, damage caused by receiving power, andso on. Note that the order of the processes of S1210 and S1216 may bereversed.

In this manner, the power transmitting apparatus 20 according to thepresent embodiment does not start transmitting a predetermined powerunless a transmission target that has been authenticated has entered adesired area where power can be supplied and the transmission targetmatches a desired transmission target. This makes it possible to preventthe emission of heat, damage due to power being transmitted, and so onin non-transmission targets. In addition, according to the presentembodiment, in the case where the power receiving apparatus 30 issupplied with power from an unauthenticated power transmittingapparatus, the power receiving apparatus 30 detects that power supplyand displays an indication thereof. Furthermore, in the case where powerhas been supplied from an unauthenticated power transmitting apparatus,the power receiving apparatus 30 can increase the receiving impedanceand prevent power from being received, making it possible to preventunnecessary power reception from an unauthenticated device and reducethe possibility of damage to the device.

Although the present embodiment describes the power transmittingapparatus 20 as starting normal power transmission in the case where thereceiving efficiency is greater than or equal to a threshold after an IDmatch notification has been detected, the normal power transmission maysimply be started after the ID match notification has been detected. Inaddition, although the power transmitting apparatus 20 determines theappropriate positional relationship with the power receiving apparatus30 based on the receiving efficiency that can be calculated from thepower received by the power receiving apparatus 30, a value aside fromthe receiving efficiency may be used for this determination as long asit is a value related to the power received by the power receivingapparatus 30. Finally, although the present embodiment describes thepower transmitting apparatus intermittently transmitting power in orderto calculate the receiving efficiency, a process for calculating thereceiving efficiency through continuous power transmission may becarried out.

Third Embodiment

The present embodiment will be described with reference to the drawings.A wireless power transmitting system according to the present embodimentis the same as the system illustrated in FIG. 1 and described in thefirst embodiment, and thus descriptions thereof will be omitted. Thepower transmitting apparatus 20 and the power receiving apparatus 30according to the present embodiment differ from those described in thefirst embodiment and the second embodiment in terms of the powertransmitting section 21 and the power receiving section 31.

When the operations performed by the power transmitting apparatus 20according to the first embodiment are taken as a first powertransmitting method and the operations performed by the powertransmitting apparatus 20 according to the second embodiment are takenas a second power transmitting method, the power transmitting apparatus20 according to the present embodiment is capable of switching betweenthe two methods. In other words, the internal configuration of the powertransmitting apparatus 20 according to the present embodiment is acombination of the configurations shown in FIGS. 2 and 8, and thusdescriptions thereof will be omitted. However, it is assumed that thepower transmitting apparatus 20 according to the present embodimentincludes a selection unit (not shown) for controlling whether to operateaccording to the first power transmitting method or the second powertransmitting method. Likewise, when the operations performed by thepower receiving apparatus 30 according to the first embodiment are takenas a first power receiving method and the operations performed by thepower receiving apparatus 30 according to the second embodiment aretaken as a second power receiving method, the power receiving apparatus30 according to the present embodiment is capable of switching betweenthe two methods. In other words, the internal configuration of the powerreceiving apparatus 30 according to the present embodiment is acombination of the configurations shown in FIGS. 3 and 9, and thusdescriptions thereof will be omitted.

Next, operations performed by the power transmitting apparatus 20 willbe described with reference to FIGS. 13 and 14. FIG. 13 is a diagramillustrating an authentication sequence between the power transmittingapparatus 20 and the power receiving apparatus 30. FIG. 14 is aflowchart illustrating operations according to the present embodiment.When starting power transmission, the power transmitting apparatus 20first carries out authentication with the power receiving apparatus 30.The power transmitting apparatus 20 issues a notification indicatingthat connection is possible, via the communication unit 22 (S1301). Thepower receiving apparatus 30, which is located in the communication area701, receives the notification indicating that connection is possible,and issues a connection request via the communication unit 32 (S1302).The power transmitting apparatus 20 sends permission to connect to thepower receiving apparatus 30 (S1303). This establishes a wireless link(S1401). Next, the power transmitting apparatus 20 sends an ID (S1304),and the power receiving apparatus 30 returns a response indicating thatthe ID has been received (S1305). The ID is determined in this manner(S1402). The foregoing has described the device authentication process.

Furthermore, the power transmitting apparatus 20 requests the powerreceiving method of the power receiving apparatus 30 (S1306). The powerreceiving apparatus 30 response to the power transmitting apparatus 20indicating whether the power receiving method of the power receivingapparatus 30 is the first power receiving method or the second powerreceiving method (S1307, S1403). In the case where the power receivingapparatus is operating according to the first power receiving method, aresponse to that effect is made (“first power receiving method” inS1404). The power transmitting apparatus 20 receives this result, sendsa power transmission start notification (S1308), and upon the powerreceiving apparatus 30 returning a response (S1309), starts transmittingpower according to the first power transmitting method (S1310, S1406).Details of the operations for transmitting power according to the firstpower transmitting method are the same as those described in the firstembodiment, and descriptions thereof will be omitted. Note that thepower transmission start notification and the response are notabsolutely necessary sequences. In the case where the power receivingmethod response (S1307) indicates that the power receiving apparatus 30is operating according to the second power receiving method (“secondpower receiving method” in S1404), the power transmitting apparatus 20starts transmitting power according to the second power transmittingmethod (S1405). Details of the operations for transmitting poweraccording to the second power transmitting method are the same as thosedescribed in the second embodiment, and descriptions thereof will beomitted.

In this manner, the power transmitting apparatus 20 according to thepresent embodiment switches between the power transmitting methodsdescribed in the first embodiment and the second embodiment based on aresponse from the power receiving apparatus 30. As a result, not only isit possible to prevent heat emission from non-power transmissiontargets, damage caused by power transmission, and so on, but it is alsopossible for a plurality of power receiving apparatuses having differentpower receiving methods to receive power. Furthermore, with the powerreceiving apparatus 30 according to the present embodiment, not only isit possible to prevent unnecessary power reception from unauthenticateddevices and reduce the possibility of damage to the device, but it isalso possible to receive power from power transmitting apparatusesoperating both in a power transmitting method that corresponds to thepower receiving method of the power receiving apparatus 30 and in adifferent power transmitting method. The foregoing has described thepower transmitting apparatus 20 requesting the power receiving methodfrom the power receiving apparatus 30 and determining the powerreceiving method according to the details of the response to thatrequest. However, which power receiving method to use in the case wherethere is no response to the request for the power receiving method fromthe power transmitting apparatus 20 may be determined in advance, andthe power receiving method may then be selected. For example, in thecase where there is no response to the power receiving method requestissued from the power transmitting apparatus 20 to the power receivingapparatus 30, “method 1” may be set between the power transmittingapparatus 20 and the power receiving apparatus 30. In this case, noresponse is returned in the case where the power receiving method of thepower receiving apparatus 30 that has received the request for the powerreceiving method in the authentication sequence is “method 1”. Becausethere is no response to the request for the power receiving method, thepower transmitting apparatus 20 transmits power according to method 1.This corresponds to a case where the power receiving apparatus 30 wishesto receive power, and thus it is often the case that the power receivingapparatus 30 does not wish to use much power. This method contributes toa reduction in the wasteful consumption of power. The same applies tothe case where “method 2” is set for cases where no response is made tothe request for the power receiving method. Selecting a commonly-usedmethod as the method used in the case where the power receivingapparatus 30 makes no response makes it possible to increase the powerreduction effects in the power receiving apparatus 30.

Fourth Embodiment

The present embodiment will be described with reference to the drawings.A wireless power transmitting system according to the present embodimentis the same as the system illustrated in FIG. 1 and described in thefirst embodiment, and thus descriptions thereof will be omitted. Thepower transmitting apparatus 20 and the power receiving apparatus 30according to the present embodiment differ from those described in thefirst embodiment and the second embodiment in terms of the powertransmitting section 21 and the power receiving section 31. Furthermore,like the power transmitting apparatus 20 and the power receivingapparatus 30 according to the third embodiment, the power transmittingapparatus 20 according to the present embodiment is capable of switchingbetween the first power transmitting method and the second powertransmitting method. In other words, the internal configuration of thepower transmitting apparatus 20 according to the present embodiment is acombination of the configurations shown in FIGS. 2 and 8, and thusdescriptions thereof will be omitted. However, it is assumed that thepower transmitting apparatus 20 according to the present embodimentincludes a selection unit (not shown) for controlling whether to operateaccording to the first power transmitting method or the second powertransmitting method. Furthermore, the power receiving apparatus 30according to the present embodiment is capable of operating according tothe first power receiving method and the second power receiving method.In other words, the internal configuration of the power receivingapparatus 30 according to the present embodiment is a combination of theconfigurations shown in FIGS. 3 and 9, and thus descriptions thereofwill be omitted.

Next, operations performed by the power transmitting apparatus 20 willbe described with reference to FIG. 15. FIG. 15 is a flowchartillustrating operations according to the present embodiment. The powertransmitting apparatus 20 establishes a wireless link with the powerreceiving apparatus 30 (S1501), and determines an ID (S1502). Up to thispoint, the power transmitting apparatus 20 is not aware of the powerreceiving method used by the power receiving apparatus 30 (that is, thefirst power receiving method or the second power receiving method). Thepower transmitting apparatus 20 starts a procedure for transmittingpower according to the second power transmitting method, using the IDdetermined in the authentication sequence (S1503). At this time, in thecase where the power receiving apparatus 30 can operate according to thesecond power receiving method, the operations are the same as thosedescribed in the second embodiment, and the power receiving apparatus 30can receive power (S1505).

On the other hand, in the case where the power receiving apparatus 30 isoperating according to the first power receiving method, the powerreceiving apparatus 30 changes the impedance based on a predetermined IDfor the power transmitted based on the ID, and thus a large disturbanceoccurs in the power transmitted by the power transmitting apparatus 20.In the case of such operations, the power transmitting apparatus 20determines that the power receiving apparatus 30 is operating accordingto the first power receiving method; the power transmitting apparatus 20then carries out intermittent transmission for ID detection according tothe first power transmitting method, and enters the same powertransmitting operations as those described in the first embodiment(S1506). Note that in the case where the power transmitting apparatus 20has first carried out a procedure for transmitting power according tothe first power transmitting method, the IDs are not exchanged in thecase where the power receiving apparatus 30 is operating according tothe second power receiving method, and thus the power transmittingprocedure does not advance.

In this manner, the power transmitting apparatus 20 according to thepresent embodiment switches between the power transmitting methodsdescribed in the first embodiment and the second embodiment based on itsown determination. As a result, in addition to preventing heat emissionfrom non-power transmission targets, damage caused by powertransmission, and so on, it is also possible for a plurality of powerreceiving apparatuses having different power receiving methods toreceive power. Furthermore, with the power receiving apparatus 30according to the present embodiment, not only is it possible to preventunnecessary power reception from unauthenticated devices and reduce thepossibility of damage to the device, but it is also possible to receivepower from power transmitting apparatuses operating both in a powertransmitting method that corresponds to the power receiving method ofthe power receiving apparatus 30 and in a different power transmittingmethod.

Other Embodiments

Embodiments of the present invention can also be realized by a computerof a system or apparatus that reads out and executes computer executableinstructions recorded on a storage medium (e.g., non-transitorycomputer-readable storage medium) to perform the functions of theabove-described embodiment of the present invention, and by a methodperformed by the computer of the system or apparatus by, for example,reading out and executing the computer executable instructions from thestorage medium to perform the functions of the above-describedembodiments. The computer may comprise one or more of a centralprocessing unit (CPU), micro processing unit (MPU), or other circuitry,and may include a network of separate computers or separate computerprocessors. The computer executable instructions may be provided to thecomputer, for example, from a network or the storage medium. The storagemedium may include, for example, one or more of a hard disk, arandom-access memory (RAM), a read only memory (ROM), a storage ofdistributed computing systems, an optical disk (such as a compact disc(CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flashmemory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2013-088878, filed Apr. 19, 2013, Japanese Patent Application No.2013-088879, filed Apr. 19, 2013, and Japanese Patent Application No.2013-088881, filed Apr. 19, 2013, which are hereby incorporated byreference herein in their entirety.

The invention claimed is:
 1. A power transmitting apparatus thattransmits power to a power receiving apparatus, the power transmittingapparatus comprising: a power transmission unit configured to executefirst wireless power transmission intermittently using a first antenna,second wireless power transmission having a power transmission periodlonger than a power transmission period of the first wireless powertransmission using the first antenna, and third wireless powertransmission having a larger amount of power than an amount of power ofthe first wireless power transmission and an amount of power of thesecond wireless power transmission using the first antenna; a detectionunit configured to detect an impedance change; and a communication unitconfigured to execute, using a second antenna different from the firstantenna, communication with the power receiving apparatus to determinewhether to execute the third wireless power transmission, wherein thepower transmission unit starts the second wireless power transmission ina case where the detection unit detects the impedance change while thefirst power transmission is executed, and the power transmission unitstarts the third wireless power transmission in a case where it isdetermined that the third wireless power transmission is to be executedby the communication by the communication unit after the second wirelesspower transmission is started.
 2. The power transmitting apparatusaccording to claim 1, further comprising: a receiving unit configured toreceive a signal received from the power receiving apparatus while thesecond wireless power transmission is executed, wherein thecommunication unit executes the communication in a case where the signalreceived by the receiving unit satisfies a predetermined condition. 3.The power transmitting apparatus according to claim 2, furthercomprising: a determination unit configured to determine whether or notan ID obtained from the signal matches a predetermined ID, and whereinthe communication unit executes the communication in a case where thedetermination unit determines that the ID obtained from the signalmatches the predetermined ID.
 4. The power transmitting apparatusaccording to claim 3, further comprising: a notification unit configuredto provide an ID match notification to the power receiving apparatus inthe case where the determination unit has determined that the IDobtained from the signal matches the predetermined ID.
 5. The powertransmitting apparatus according to claim 3, wherein the ID isdetermined by the determination unit in device authentication carriedout between the power transmitting apparatus and the power receivingapparatus.
 6. The power transmitting apparatus according to claim 2,wherein the signal is load modulated.
 7. The power transmittingapparatus according to claim 1, wherein the communication unitcommunicates a value related to power received by the power receivingapparatus, and wherein the power transmitting apparatus determineswhether or not to execute the third power transmission based on thevalue.
 8. The power transmitting apparatus according to claim 7, whereinthe power transmitting apparatus determines to execute the third powertransmission in a case where the value is greater than or equal to athreshold value.
 9. The power transmitting apparatus according to claim1, further comprising: an obstacle detection unit configured to detectan obstacle; and a display unit configured to display an error messagein the case where the obstacle has been detected by the obstacledetection unit.
 10. The power transmitting apparatus according to claim1, wherein the communication unit communicates by the Bluetooth.
 11. Acontrol method for a power transmitting apparatus that transmits powerto a power receiving apparatus, the method comprising: executing firstwireless power transmission intermittently using a first antenna, secondwireless power transmission having a power transmission period longerthan a power transmission period of the first wireless powertransmission using the first antenna, and third wireless powertransmission having a larger amount of power than an amount of power ofthe first wireless power transmission and an amount of power of thesecond wireless power transmission using the first antenna; detecting animpedance change; and executing, using a second antenna different fromthe first antenna, communication with the power receiving apparatus todetermine whether to execute the third wireless power transmission,wherein the second wireless power transmission is started in a casewhere the impedance change is detected while the first powertransmission is executed, and the third wireless power transmission isstarted in a case where it is determined that the third wireless powertransmission is to be executed by the communication after the secondwireless power transmission is started.
 12. A non-transitorycomputer-readable storage medium storing a program that causes acomputer to: execute first wireless power transmission intermittentlyusing a first antenna, second wireless power transmission having a powertransmission period longer than a power transmission period of the firstwireless power transmission using the first antenna, and third wirelesspower transmission having a larger amount of power than an amount ofpower of the first wireless power transmission and an amount of power ofthe second wireless power transmission using the first antenna; detectan impedance change; and execute, using a second antenna different fromthe first antenna, communication with the power receiving apparatus todetermine whether to execute the third wireless power transmission,wherein the program causes the computer to start the second wirelesspower transmission in a case where the impedance change is detectedwhile the first power transmission is executed, and to start the thirdwireless power transmission in a case where it is determined that thethird wireless power transmission is to be executed by the communicationafter the second wireless power transmission is started.